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Surface Melting in Alkane Emulsion Droplets as Affected by Surfactant Type
Author(s) -
Gülseren İbrahim,
Coupland John N.
Publication year - 2008
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-008-1216-z
Subject(s) - pulmonary surfactant , octadecane , crystallization , nucleation , melting point , alkane , emulsion , chemistry , chemical engineering , chromatography , materials science , crystallography , hydrocarbon , organic chemistry , engineering , biochemistry
The influence of surfactant type (Tween 20, Tween 40, Tween 60, Tween 80, Brij 58, Triton X‐100, SDS, STS) on the crystallization and melting characteristics of emulsified (mean droplet diameter 0.52 μm) n ‐octadecane and n ‐eicosane were studied using microcalorimetry. The melting point (~37 °C) of the eicosane droplets was higher than the crystallization point (~24 °C) and was not affected by the surfactant selected. There was a similar separation between the crystallization (~14 °C) and melting (~28 °C) point of the emulsified octadecane however the details of the transitions was affected by the surfactant selected. For Tween 40 and Brij 58‐stabilized droplets there was a split peak on crystallization which we attribute to a surface heterogeneous nucleation mechanism. Only these surfactant‐alkane combinations had a split peak on melting. The size of the lower temperature fraction decreased with droplet size suggesting another surface effect. However, the size of the surface layer was calculated to be many times the length of the surfactant tail suggesting the crystal structure was modified by the nucleation mechanism.